The maximum output power of AlGaAs lasers is generally limited by irreversible mirror damage that begins at a defined light power density. For enhancing output power, the emission surface of the laser can be broadened parallel to the active zone, so that the emitted light power increases for the same maximum power density. Several approaches of accomplishing this are, for example, laser array structures having a plurality of optically coupled individual stripe lasers or what are referred to as broad stripe lasers. These laser structures generally have the property that a plurality of lateral modes of the broad structure can be propagated and resonated simultaneously. This results in broad, lateral far zones having a plurality of lobes. A diffraction-limited imaging for small spot diameters is not possible with such lateral multi-mode structures.
There are a number of array structures that have large mode selection for the lateral fundamental mode. However, a stable lateral mode can be maintained over a large power spectrum only with difficulty because of technical irregularities and because of the significant interaction of light power and wave guidance.
U.S. Pat. No. 4,713,821 discloses a semiconductor laser that is composed of a laser region having an active laser stripe and of an intensification region separated therefrom by a narrow coupling region, the active layer being trapezoidal and broadened in this intensification region. The radiation coupled out in the intensification region is laterally widened and emerges from the component at an end face. This component is manufactured such that a substrate with semiconductor layers grown thereon is secured to a planar reference surface and is then cleaved along a lattice plane that forms the boundary between the laser region and the intensification region. The cleaving results in the structure having a coupling region.
U.S. Pat. No. 4,773,076 discloses a semiconductor laser wherein a continuous waveguide is fashioned as an active layer having a different width in two different regions. FIG. 1B of this patent shows the lateral dimensioning of the active layer with broken lines. The second region that is present therein does not serve as an intensification region but as a second laser resonator that is coupled with the first laser resonator. This results in a laser divided into two regions having different resonator properties because of the continuously proceeding active layer and correspondingly present resonator end faces.